Answer :
The Red Scare was the fear of communism spreading into the United States. This scare came in two "waves": the first after WWI and the second in the post- WWII period during Eisenhower's presidency. Communism first became a problem after dictator and communistic governments developed in Europe along with Bolsheviks, anarchists, labor unions and immigrants. Then as WWII ended and tensions increased between the USSR and U.S. in the Cold War, American citizens then grew extremely cautious over communism in America over spies and traitors helping the USSR. One great example of this cautiousness is Joseph McCarthy's use of his McCarthyism to exploit communists in America through extreme measures. Some of his McCarthyistic views lead to formation of groups such as HUAC(House Un-American Activities Committee) to support him.
A fear that communists and radicals were plotting revolution in the United States
